High strength alloy of the cu-al-be series



United States Patent 3,459,544 HIGH STRENGTH ALLOY OF THE Cu-Al-Be SERIES Seizo Watanabe, 61 Shinomiya-jutaku, 58 Kamishimagashira, Kadoma-cho, Kadoma-gnn, Osaka-fa, Japan No Drawing. Continuation-impart of application Ser. No. 317,888, Oct. 22, 1963. This application Jan. 17, 1967, Ser. No. 609,789

Claims priority, application Japan, Nov. 9, 1962, 32/ 50,442 Int. Cl. C22c 9/00 U.S. Cl. 75162 2 Claims ABSTRACT OF THE DISCLOSURE An alloy of the Cu-Al-Be series particularly suitable for the propeller of a high speed ship, consisting essentially by weight, aluminum 8.6 to 9.8 percent, beryllium being present in proportion to said aluminum according to a fixed percentage, and the balance being copper. In a modified form there may be present small percentages of nickel, iron, cobalt, titanium, molybdenum chromium, and manganese. This alloy has excellent castability, and workability, excellent tensile strength, and more than fifteen percent elongation as cast, and excellent cavitation erosion resistance.

This invention relates to an alloy of the Cu-Al-Be series.

This application is a continuation-in-part of my copend ing application, Ser. No. 317,888, filed Oct. 22, 1963, now abandoned for An Alloy of The Cu-Al-Be Series.

It is necessary that an alloy for use in the propeller for a high speed ship, the impeller for various kinds of pumps, and the water Wheel for an electric generator, should have a high mechanical strength, an excellent corrosion resistance, and particularly a superior cavitation erosion resistance.

Heretofore, it has been well known that such alloys as high tensile brass, nickel aluminum bronze, and stainless steel, having such compositions and properties as are here shown in Table I, are available for such purposes as above enumerated.

TABLE I High tensile Ni Al Stainless brass bronze steel Chemical composition, percent However, these requirements, particularly as to the cavitation erosion resistance, have not yet been satisfied 3,459,544 Patented Aug. 5, 1969 by such well known alloys, so that in fact some damage has been frequently caused by cavitation erosion. Under these circumstances, the development of more suitable material for the above stated usages has been looked for.

The object of this present invention is to overcome such drawbacks as mentioned above and to provide an alloy to meet such need.

In accordance with one aspect of this present invention, there is provided an alloy of the Cu-Al-Be series consisting essentially of aluminum, beryllium, and copper, the aluminum content weighing 8.6 to 9.8 percent, the beryllium content weighing in proportion to the aluminum so as to satisfy the following equation.

Percentage by weight of Be=(l:0.2) (3.060.28 percentage by weight of Al) and the copper being the balance. The alloy may additionally contain a minor quantity or minor quantities of nickel, iron, cobalt, titanium, molybdenum, chromium, and/or manganese, conditional on the proportions of aluminum and beryllium being as above.

The alloy in accordance with this present invention has (1) an excellent castability and workability, (2) such superior mechanical properties as more than 55 kg./mm. in tensile strength and more than 15 percent in elongation as cast, and (3) an extremely excellent cavitation erosion resistant property.

Applicant has studied experimentally various compositions belonging to this Cu-Al-Be series with respect to their mechanical properties, microstructures, and cavitation erosion resistances. In studying the cavitation erosion resistance, a magnetostriction vibrative-system cavitation erosion tester was used at 6000 cycles per second, the results thereof stated hereinafter being expressed by the unit of mg. per minutes, which is the reduction in weight due to cavitation erosion. The elements covered in this study were copper, beryllium, aluminum, nickel, iron, cobalt, titanium, molybdenum, manganese, and chromium. The ranges of proportions in the alloy of these elements were as follows:

Percent Cu to 53 Be 0 to 4 Al 0 to 15 Ni 0 to 5 Fe 0 to 5 Co 0 to 5 Ti 0 to 1 Mo 0 to 5 Mn 0 t0 5 Cr 0 t0 2 It has been found experimentally that when less than 8.6 percent of aluminum was alloyed into beryllium and copper, it is impossible to obtain an alloy having an excellent resistance against cavitation erosion. For example, the following is experimental data showing the fact.

Referential data 1 An alloy whose composition was 6.91 percent of aluminum, 0.98 percent of beryllium, and the balance copper was prepared. Its tensile strength was 56.3% kg./mm. and its elongation was 18.8 percent. However, its reduction in weight due to cavitation erosion was 8.9 mg.

which is not particularly excellent comparing with the conventional alloys, even though the proportion of beryllium to aluminum lies within the range defined in accordance with this present invention.

This would be derived from the small content of aluminum so that it is necessary to alloy at least 8.6 percent of aluminum. On the other hand, it has also been found experimentally that when more than 9.8 percent of aluminum was alloyed into beryllium and copper, it is impossible to obtain an alloy having an elongation of more than 15 percent. In this case, although it is possible to obtain an alloy having a high strength and a high resistance against cavitation erosion, it is impossible to improve the alloy with respect to elongation. For example, the following is experimental data showing the fact.

Reference data 2 An alloy whose composition was 10.25 percent of aluminum, 0.27 percent of beryllium, and the balance copper, was prepared. Its tensile strength was 55.0 kg./mm. and its reduction in weight due to cavitation erosion was 1.2 mg. However, its elongation was such a low value as 10.5 percent, notwithstanding the proportion of beryllium to aluminum lay within the range defined depending upon the proportion of aluminum in accordance with this present invention.

It is considered that such a low elongation would be derived from the excess of aluminum. Thus it has been found that it is necessary to limit the proportion of aluminum within a range of from 8.6 percent to 9.8 percent for satisfying the requirements of obtaining an alloy having such mechanical properties as a tensile strength of more than 55 kg./mm. and an elongation of more than 15 percent and, at the same time, an appreciably more excellent resistance against cavitation erosion than those in accordance with the prior art.

For alloying beryllium into aluminum and copper where aluminum weighs between 8.6 percent and 9.8 percent as above, it has been experimentally found that there must be a determined proportion of beryllium to aluminum in order to obtain an alloy having excellent mechanical properties in addition to a superior resistance against cavitation erosion. The proportion is represented by the following equation as stated hereinbefore:

Percent by weight of Be=(1:0.2)(3.060.2'8 percentage by weight of A1) If the proportion of beryllium to aluminum content exceeds the range defined as above, such alloys which have disadvantageously low elongation would be obtained. If the proportion of beryllium to aluminum comes short of the definition in accordance with this present invention, such alloys which are lacking in tensile strength would be obtained. The following data show such experimental facts.

Referential data 3 An alloy whose composition was 7.44 percent of aluminum, 1.27 percent of beryllium, and the balance copper was prepared, notwithstanding it is necessary to alloy beryllium in the proportion between 1.17 and 0.74 to 7.44 percent of aluminum. By virtue of the excess of beryllium, the elongation of the alloy was 12.8 percent which does not satisfy the requirement, while the tensile strength was 69.5 kg./mm. and the reduction in weight due to cavitation erosion was 2.1 mg.

Referential data 4 An alloy whose composition was 8.72 percent of aluminum, 0.88 percent of beryllium, and the balance copper was prepared, notwithstanding it is necessary to alloy beryllium in the proportion between 0.74 and 0.50, to 8.72 percent of aluminum. By virtue of the excess of beryllium, the elongation of the alloy was 14.2 percent while the tensile strength was 67.0 kg./mm. and the reduction in weight due to cavitation erosion was 1.6 mg.

Referential data 5 An alloy whose composition was 9.52 percent of aluminum, 0.51 percent of beryllium, and the balance copper, was prepared, notwithstanding it is necessary to alloy the beryllium in the proportion between 0.46 and 0.32 to 9.53 percent of aluminum. By virtue of the excess of beryllium, the elongation of the alloy was 13.4 while the tensile strength was 59.4 kg./mm. and the reduction in weight due to cavitation erosion was 1.2 mg.

Referential data 6 An alloy whose composition was 8.02 percent of aluminum, 0.59 percent of beryllium, and the balance copper was prepared. Notwithstanding it is necessary to alloy the beryllium in the proportion between 0.98 and 0.61 to 8.02 percent of aluminum. By virtue of the small content of beryllium, the tensile strength of the alloy was 53.3 which is smaller than the required value 55 kg./mm. while the elongation was 32.7 percent and the reduction in weight due to cavitation erosion was 3.7 mg.

Referential data 7 An alloy whose composition was 9.38 percent of aluminum, 0.20 percent of beryllium, and the balance copper was prepared, notwithstanding it is necessary to alloy the beryllium in the proportion between 0.52 and 0.35, to 9.38 percent of aluminum. By virtue of the small content of beryllium, the tensile strength of the alloy was 52.6 kg./mm. while the elongation was 35.2 percent and the reduction in weight due to cavitation erosion was 2.6 mg.

Applicant has also studied such secondary elements as nickel, iron, cobalt, titanium, molybdenum, chromium, and manganese. These elements may be contained in copper to be alloyed in accordance with this present invention. They may be individually maintained below upper limits 1.0 percent of nickel, 0.5 percent of iron, 0.3 percent of cobalt, 0.5 percent of titanium, 0.3 percent of molybdenum, 0.8 percent of chromium, and 1.5 percent of manganese. They may coexist within the above limits. In general, they affect the alloy advantageously, but the necessary proportion of aluminum and that of beryllium to aluminum are not affected by these secondary elements.

The invention is further disclosed in the following examples, which are illustrative but not limitative thereof.

EXAMPLE 1 An alloy whose composition was 8.86 percent of aluminum, 0.55 percent of beryllium, and the balance copper was prepared. The percentage 0.55 for beryllium lay within a range between 0.695 and 0.463, for 8.86 percent of aluminum in accordance with this present invention. The tensile strength of the alloy was 60.1 kg./mm. The elongation thereof was 26.6 percent. The reduction in weight due to cavitation erosion thereof was 1.3 mg.

EXAMPLE 2 An alloy whose composition was 9.11 percent of aluminum, 0.46 percent of beryllium, and the balance copper was prepared. The percentage 0.46 for beryllium lay within a range between 0.611 and 0.407, for 9.11 percent of aluminum in accordance with this present invention. The tensile strength of the alloy was 56.8 kg./mm. The elongation thereof was 28.0 percent. The reduction in weight due to cavitation erosion was 1.25 mg.

EXAMPLE 3 An alloy whose composition was 9.69 percent of aluminum, 0.34 percent of beryllium, and the balance copper, was prepared. The percentage 0.34 for beryllium lay within a range between 0.416 and 0.277, for 9.69 percent of aluminum in accordance with this present invention. The tensile strength of the alloy was 58.2 kg./mm. The elongation thereof was 20.3 percent. The reduction in weight due to cavitation erosion there was 1.2 mg.

5 =What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An alloy of the Cu-Al-Be series consisting essentially of by Weight aluminum 8.6 to 9.8 percent, beryllium being present in proportion to said aluminum so as to satisfy the following equation; percentage by weight of aluminum=(l 0.2) (3.06-0.28 percentage by weight of aluminum), and the balance copper, said alloy being characterized by tensile strength of more than 55 kg./ mm. and an elongation of more than 15% as cast, and excellent cavitation erosion resistant properties.

2. An alloy of the Cu-Al-Be series as claimed in claim 1, which contains in addition at least one member of the group consisting of up to 1.0 percent nickel, up to cent titanium, up to 0.3 percent molybdenum, up to 0.8 percent chromium, and up to 1.5 percent manganese, respectively.

References Cited UNITED STATES PATENTS 2,400,234 5/1946 Hudson 75-162 X FOREIGN PATENTS 750,302 4/1933 France. 464,424 7/ 1951 Italy.

CHARLES N. LOVELL, Primary Examiner U.S. Cl. X.R.

0.5 percent iron, up to 0.3 percent cobalt, up to 0.5 per- 15 75153 

